Research Interests

Theoretical study of inelastic and reactive molecular collisions, particularly those involving free radicals; the photofragmentation of small molecules; and the structure and energetics of weakly bound complexes involving open-shell species.

Kirwan Faculty Research and Scholarship Prize, University of Maryland, 1999

Elected Fellow, American Association for Advancement of Science, 2012

Elected Member, International Academy of Quantum Molecular Science, 2015

Herschbach Medal, Dynamics of Molecular Collisions, 2015

Research

Chemistry in most combustion environments involves atoms and small molecular radicals. An understanding of the chemical kinetics and relaxation pathways in conditions far from equilibrium depends critically on our ability to model accurately inelastic and reactive collisions involving radicals. Alexander’s work has provided a framework for the understanding of these processes. Utilizing state-of-the art techniques in ab initio quantum chemistry and new methods in quantum collision theory, he has pushed forward the frontier in the understanding of how electronic and nuclear motion are coupled in elementary inelastic and reactive collisions.

Alexander’s earlier work on inelastic scattering of open-shell molecules enabled the understanding of a numerous experimental studies on these systems. Similarly, his recent work on non-adiabatic effects in the paradigm F+H2, Cl+H2, and O+H2 reactions has transformed our understanding of a wealth of experimental work on these elementary reactions. The figure below illustrates how the unpaired electrons on the O atom evolve in its reaction with molecular hydrogen, 1 a reaction probed recently in crossed molecular-beam scattering studies by Minton, McKendrick and co-workers. 2

The impact of Alexander’s work on the field of chemical dynamics is witnessed by his co-authorship of one paper in Physical Review Letters, 3 five papers in Science, and one paper in Nature Chemistry since 2001. 4–8 His research has been the subject of two accompanying Science perspective articles. 9,10 The overall relevance to the broader physics and chemistry communities has been underlined by the appearance of general interest reports of Alexander’s work in the professional journals Physics Today, 11 World of Chemistry, 12 and Chemical and Engineering News. 13